Biology Reference
In-Depth Information
Chapter 7
Sonic Patterns II: The Animal Choruses
Choruses are one of the most mysterious and spectacular acoustic phenomena
common to terrestrial and aquatic biomes. Choruses are the result of contemporary
vocalization of several individuals and species at a precise time of the day (dawn or
dusk).
Several hypotheses have been presented during recent years. First, the beginning
of the chorus activity is species specific and can be explained by body size and
eye size.
Intrinsic factors, environmental factors, and social factors can concur in the
chorus performance.
Among the several hypotheses to explain this phenomenon, the acoustic trans-
mission hypothesis has received much credit. This hypothesis claims a more
favorable condition of acoustic transmission at dawn and at dusk for a quieter
atmosphere and the lowest background noise. Reduced foraging efficiency at dawn
and at dusk and an excess of food storage the day before are further good
arguments.
In amphibians choruses are very common, energetically costly, and occur
especially during the short reproductive period. In frogs, a cooperative hypothesis
according to which a chorus produces benefits in the entire population is opposed to
a competitive hypothesis in which a leading caller is preferred in sexual selection.
In fact, it has been demonstrated that females are attracted by leading and loud
signals.
In birds, there is considerable evidence that choruses can be explained by at least
two major hypotheses: an energetic hypothesis and a behavioral hypothesis.
According to the first hypothesis, the choruses are performed in coincidence with
a food surplus or fat reserves. The second hypothesis considers the choruses as an
interactive communication between concurrent males that seem to be a reaction to
the past day's vocal interactions between males.
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